By Jinsu Chang By Jinsu Chang

6.3.1 define pathogen6.3.1 define pathogen

Pathogen is "any living organism or virus that is capable of causing a disease" 

BacteriaBacteria

ProtozoaProtozoa

VirusVirus

FungiFungi

6.3.2 Explain why antibiotics are 6.3.2 Explain why antibiotics are effective against bacteria but not effective against bacteria but not

against pathogensagainst pathogens

• Bacteria are Prokaryotic cells

• Somatic cells (body cells) are Eukaryotic cells

• Prokaryotic cells and eukaryotic cells have different biochemical reactions and pathways

• They both have a different structure (Prokaryotes have a cell wall made of Peptidoglycan body cells don’t)

• Antibiotics are chemicals that take advantage of the difference between the two!!!!

• *No effect on Virus!

THERE ARE MANY WAYS ANTIBIOTICS THERE ARE MANY WAYS ANTIBIOTICS TAKE ADVANTAGE OF THE TAKE ADVANTAGE OF THE

DIFFERENCE BETWEEN EUK AND DIFFERENCE BETWEEN EUK AND PROKPROK

Selectively block protein Selectively block protein synthesis in bacteria, but no synthesis in bacteria, but no

effect on body cellseffect on body cells

Inhibit the production of new cell Inhibit the production of new cell wall by bacteria, which block wall by bacteria, which block

ability to grow and divide through ability to grow and divide through binary fissionbinary fission

Preventing the entrance of Preventing the entrance of pathogens to our bodypathogens to our body

“It is best to prevent than to cure”

There are many ways to prevent entrance of pathogens:

1) Stay away from sources of infection

2) Human body is designed to protect us from pathogens because it is obviously impossible to stay away from all pathogens

SkinSkin

Skin is a barrier to infection

DermisDermisThe underneath layer of the skin

is very much alive. It contains sweat glands, capillaries, sensory receptors and dermal cells that

give structure and strength to the skin.

EpidermisEpidermisThe layer on top of the dermis. Epidermal layer is constantly

replaced as underlying dermal cells die and are moved upwards.

Stomach AcidStomach AcidThe layer on top of the dermis. Epidermal layer is constantly

replaced as underlying dermal cells die and are moved upwards.

Scab FormationScab FormationBlood Clotting and scab formation stops pathogens from getting in.

TearsTearsTears are antiseptic and kill

microbes (pathogens)

MucusMucus

Mucus can trap incoming pathogens and so prevent from reaching cells they could infect.

Some Mucus membrane are lined with cilia, which are hair-like extensions capable of a wave-like movement. This movement moves trapped pathogens up and out of mucous-lined tissues.

Area with mucous membrane

What it is and does

Trachea Tube which carries air to and from the lungs

Nasal Passages Tubes which allow air to enter the nose and then the trachea

Urethra Tube which carries urine from bladder to the outside

Vagina Reproductive tract leading from uterus to the outside

TracheaTrachea

Nasal PassagesNasal Passages

Role of phagocytic Role of phagocytic LeucocytesLeucocytes

Leucocytes are the cells in our bloodstream that help us fight off pathogens that enter our bodies and also provide us with an immunity for many pathogens we encounter a second time.

Macrophage Macrophage Macrophages are

large white blood cells that are able to change their cellular shape to surround an invader and take it in through phagocytosis.

*Macrophages can easily change their shape. Thus they are able to squeeze their way in and out of capillaries.

MacrophageMacrophage

Recognizes whether the cell is a natural part of the body and therefore ‘self’ or not part of the body and therefore ‘not-self.’

Recognition is based on protein molecules that make up part of the surface of all cells and viruses (antigens).

*Doesn’t recognize which pathogen it is, just determine is ‘self’ or ‘not self’

Macrophages in ActionMacrophages in Action

Macrophage in ActionMacrophage in Action

Antibodies are produced in Antibodies are produced in response to a specific response to a specific

pathogenpathogen

Leucocytes that produce antibodies are called B lymphocytes.

There are many types of B lymphocytes and each B lymphocyte can produce only one type of antibodies.

Antibodies vs AntigenAntibodies vs Antigen

Steps of a typical Steps of a typical Immune responseImmune response

1. A specific antigen type is identified

2. A specific B lymphocyte is identified that can produce an antibody which will bind to the antigen

3. The B lymphocyte and several identical B lymp. Clone themselves to increase the number of the same type of B lymp.

4. The newly formed ‘army’ begins antibody production

5. Newly released antibodies circulate in the bloodstream and eventually find their antigen match

6. Using various mechanisms, the antibodies help eliminate the pathogen

7. Some of the cloned B lym. remain and give immunity from a second infection by the same pathogen.

HIV invades Helper T-HIV invades Helper T-cellscells

Risk Factors in HIV Risk Factors in HIV transmissiontransmission

• No risk:– Skin Contact– Toilet Seats– Mosquitoes

• Low Risk:– Saliva/kissing– Ingestion– Childbirth

• High Risk:– Breast feeding– -Sexual Intercourse– -Blood-Blood contact

Social Implications of Social Implications of AIDSAIDS

Social Impacts: Discrimination and stigma from those around Abuse and harrassment May not be able to find work May not be healthy enough to work Expense of medications bankrupts families Risk of spreading in a family or community Burden of care for the sick